ML082950468

Nine-Month Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems

ML082950468
Person / Time
Site:	San Onofre
Issue date:	10/14/2008
From:	Short M P Southern California Edison Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-08-001
Download: ML082950468 (33)

Text

SOUTHERN CALIFORNIA Michael P. Short F EDISON Vice President An EDISON INTERNATIONAL Company October 14, 2008 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Docket Nos. 50-361 and 50-362 Nine-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" San Onofre Nuclear Generating Station, Units 2 and 3

References:

See Attachment 1

Dear Sir or Madam:

The Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2008-01 (Reference

1) to request that each licensee evaluate its licensing basis, design, testing, and corrective action programs for the emergency core cooling, decay heat removal, and containment spray systems to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified.

The NRC, in GL 2008-01, requested each licensee to submit a written response in accordance with 10 CFR 50.54(f) within nine months of the date of the GL to provide the following information: (a) A description of the results of evaluations that were performed pursuant to the requested actions of the GL. This description should provide sufficient information to demonstrate that you are or will be in compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems of the GL;(b) A description of all corrective actions, including plant, programmatic, procedure, and licensing basis modifications that you determined were necessary to assure compliance with these regulations; and, P.O. Box 128 San Clemente, CA 92674-0128 (949) 368-3780 Fax: (949) 368-3770 Document Control Desk-2-October 14, 2008 (c) A statement regarding which corrective actions were completed, the schedule for completing the remaining corrective actions, and the basis for that schedule.Attachment 2 to this letter contains the Southern California Edison (SCE) Nine-Month response to the requested information in GL 2008-01.Corrective Actions are provided in Section B of Attachment

2. SCE considers these Corrective Actions to be regulatory commitments.

SCE submitted a three-month response (Reference

2) indicating it would complete its GL evaluation and provide the results in its Nine-Month response.

As identified in SCE's supplemental three-month response (Reference 4), the evaluation is based on walkdowns completed prior to issuance of GL 2008-01 and design configuration control.SCE has, however, decided that confirmatory walkdowns to support the GL response would be prudent. These walkdowns are not yet complete as discussed in Attachment

2. Due to the effort to add conservatism to the methodology applied in the evaluation, any differences found during the walkdowns are not expected to change the evaluation results. Regulatory commitments to complete these walkdowns and provide Nine-.Month supplemental responses are provided as Corrective Actions in Section B of.Attachment 2.Should you have any questions, please contact Ms. Linda Conklin at (949) 368-9443.I declare under penalty of perjury that the foregoing is true and correct.Executed on I)- 1... ZoO" Document Control Desk October 14, 2008 Attachments:

1. References

2. Nine-Month Response to NRC Generic Letter (GL) 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" cc: E. E. Collins, Regional Administrator, NRC Region IV N. Kalyanam, Project Manager, SONGS Units 2 and 3 G. G. Warnick, NRC Senior Resident Inspector, San Onofre Units 2 & 3 Attachment 1 References

1. NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11, 2008 2. May 15, 2008 letter from R. Ridenoure (SCE) to Document Control Desk (NRC),

Subject:

Three-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," San Onofre Nuclear Generating Station Units 2 and 3 3. August 12, 2008 letter from N. Kalyanam (NRC) to R. Ridenoure (SCE),

Subject:

San Onofre Nuclear Generating Station Units 2 and 3 -Generic Letter 2008-01,"Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," Proposed Alternative Course of Action (TAC NOS. MD7876 and MD 7877)4. September 12, 2008, letter from J. T. Reilly (SCE) to Document Control Desk (NRC),

Subject:

Supplement to Three-Month Response to NRC Generic Letter 2008-01,"Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," San Onofre Nuclear Generating Station, Units 2 and 3 Page 1 of 1 Attachment 2 Nine-Month Response to NRC Generic Letter (GL) 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" This attachment contains Southern California Edison's (SCE's) Nine-Month response for the San Onofre Nuclear Generating Station (SONGS) Units 2 and 3 to NRC Generic Letter (GL) 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11, 2008. In GL 2008-01, the NRC requested "that each addressee evaluate its ECCS, DHR system, and containment spray system licensing basis, design, testing, and corrective actions to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified." The following information is provided in this response: a) A description of the results of evaluations that were performed pursuant to the requested actions (see Section A of this Attachment), b) A description of the corrective actions determined necessary to assure compliance with the quality assurance criteria in Sections III, V, Xl, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license with respect to the subject systems (see Section B of this Attachment), and c) A statement regarding which corrective actions have been completed, the schedule for the corrective actions not yet complete, and the basis for that schedule (see Section B of this Attachment).

The following systems were determined to be in the scope of GL 2008-01 for SONGS: " Emergency Core Cooling System (ECCS)* Shutdown Cooling System (SDCS)" Containment Spray System (CSS)Page 1 of 29 Attachment

2 Background

SCE has taken action to manage gas intrusion into the ECCS prior to the issuance of GL 2008-01 and is continuing with previously planned equipment upgrades to reduce potential gas intrusion.

In 1999 SCE identified gas intrusion into the ECCS discharge headers at SONGS as an issue. Gas intrusion in this system occurs when nitrogen-saturated water from the pressurized Safety Injection Tanks (SITs) leaks through the containment check valves into the lower pressure ECCS discharge headers. It was recognized that gas intrusion into the discharge lines could result in a water hammer when ECCS is actuated.

SCE monitors the gas volume and limits the accumulation to preclude a potential water hammer event.SCE calculation M-DSC-370, "LPSI/HPSI

[Low Pressure Safety Injection/High Pressure Safety Injection]

Nitrogen Pocket Transient Analysis" (Reference

5) determined the limiting void size to preclude water hammer in the low pressure discharge line as documented in Action Requests 991000890 (Reference

45) and 001200671 (Reference 46).SCE monitors the level in the SITs to quantify and trend the amount of gas accumulation in the ECCS discharge headers and ensure the leakage past the containment check valves does not exceed the allowable limits. Henry's Law is used to evaluate the level drop and quantify the amount of nitrogen coming out of solution to ensure the water hammer evaluation is not challenged.

As part of this effort, five (5) vent valves per unit were added to the high points of the ECCS where vents did not exist. These five vents were also added to procedure S023-3-3.8, "Safety Injection Monthly Tests," (Reference

17) to monitor the identified gas intrusion path.Prior to the issuance of GL 2008-01, SCE planned to install new soft-seated check valves designed to reduce the amount of gas intrusion (back leakage) from the SITs.The new valves are being phased in as maintenance replacements for the existing valves.Page 2 of 29 Attachment 2 A. EVALUATION RESULTS Licensing Basis Evaluation SCE reviewed the SONGS licensing basis with respect to gas accumulation in the Emergency Core Cooling, Shutdown Cooling, and Containment Spray Systems. This review included the Technical Specifications (TS), TS Bases, Updated Final Safety Analysis Report (UFSAR), the Licensee Controlled Specifications (LCS) and LCS Bases, responses to NRC generic communications, Regulatory Commitments, and License Conditions.

1. Summary of the results of the review of these documents:

The above documents and regulatory commitments were evaluated for compliance with applicable regulatory requirements.

The following TS, Surveillance Requirements (SR) and UFSAR sections pertain to GL 2008-01: a) TS 3.5.2, ECCS -Operating, SR 3.5.2.4, "Verify ECCS piping is full of water." Frequency:

31 days Bases for SR 3.5.2.4: "The ECCS pumps are normally in a standby, nonoperating mode. As such, flow path piping has the potential to develop voids and pockets of entrained gases. Maintaining the piping from the ECCS pumps to the RCS [Reactor Coolant System] full of water ensures that the system will perform properly, injecting its full capacity into the RCS upon demand. This will also prevent water hammer, pump cavitation, and pumping of noncondensible gas (e.g., air, nitrogen, or hydrogen) into the reactor vessel following an SIAS [Safety Injection Actuation Signal] or during SDC. The 31 day Frequency takes into consideration the gradual nature of gas accumulation in the ECCS piping and the adequacy of the procedural controls governing system operation." b) TS 3.6.6.1, Containment Spray and Cooling Systems, SR 3.6.6.1.4, "Verify the containment spray piping is full of water to within 10 feet of the lowest spray ring." Frequency:

24 months Bases for SR 3.6.6.1.4: "Verifying that the containment spray header piping is full of water to within 10 feet of the lowest spray ring minimizes the time required to fill the header." c) UFSAR 5.4.7, Residual Heat Removal System i. Section 5.4.7.1.2, Design Criteria, paragraph B, states the shutdown cooling initiation pressure.Page 3 of 29 Attachment 2 ii. Section 5.4.7.2.2, Equipment and Component Descriptions, Item D, Valves, last paragraph, states the shutdown cooling relief valves'setpoints.

d) UFSAR 6.2.2, Containment Heat Removal Systems, Section 6.2.2.1.2.3, System Operations, Tables 6.2-30 and 6.2-31, in the Basis column, state"The containment spray header riser is filled with water to within 10 feet of the first ring header to improve spray start times." e) UFSAR 6.2.2, Containment Heat Removal Systems, Section 6.2.2.1.3, Design Evaluation, states "An analysis of the effects of water hammer in the dry portion of the spray rings has been performed." f) UFSAR 6.3, Emergency Core Cooling System, Section 6.3.2.2.4, Piping i. Paragraph E states "All ECCS lines will be maintained during normal operation in a filled condition." ii. Paragraph F states "The Safety Injection pump suction line from the containment emergency sump will be maintained during normal operation in a filled condition up to the containment isolation valves located outside containment." 2. Summary of the changes to licensing basis documents:

SCE has not made any changes to licensing basis documents as a result of the Generic Letter evaluation.

3. Items that have not been completed, schedule for their completion, and the basis for that schedule: SCE will make one change to the TS Bases for SR 3.5.2.4. The phrase"Maintaining the piping from the ECCS pumps to the RCS full of water..." will be changed to read "Maintaining the piping from the RWST [Refueling Water Storage Tank] to the RCS full of water..." This clarification makes the Bases consistent with the procedure that performs the surveillance which includes both suction and discharge piping. This Bases change will be tracked as a Corrective Action resulting from the Generic Letter evaluation and will be completed no later than 90 days after the Unit 3 Cycle 15 outage scheduled for October 2008. See Section B, Item 1, of this Attachment.

TS improvements are being addressed by the Technical Specification Task Force (TSTF) to provide an approved TSTF traveler for making changes to individual licensee's TS related to the potential for unacceptable gas accumulation.

The development of the TSTF traveler relies on the results of the evaluations of a large number of licensees to address the various plant designs.SCE is continuing to support the industry and NEI Gas Accumulation Management Team activities regarding the resolution of generic TS changes via Page 4 of 29 Attachment 2 the TSTF traveler process. Following NRC approval of this TSTF, SCE will evaluate adopting the TSTF to either supplement or replace current TS and LCS requirements.

SCE will track the TSTF evaluation as a Corrective Action resulting from the Generic Letter evaluation which will be completed no later than 1 year after NRC approval of the TSTF. See Section B, Item 6, of this Attachment.

Page 5 of 29 Attachment 2 Design Evaluation SCE reviewed the SONGS design basis to identify sources of gas intrusion and areas with potential for gas accumulation in the Emergency Core Cooling, Shutdown Cooling, and Containment Spray Systems. This review included Design Basis Documents, Calculations, Drawings, Engineering Evaluations, and Vendor Technical Documents.

1. Results of the review of the design basis documents:

The following key design basis documents were reviewed in response to GL 2008-01: a) Technical Specifications

-See the Licensing Basis Evaluation section of this Attachment.

b) Updated Final Safety Analysis Report (UFSAR) -See the Licensing Basis Evaluation section of this Attachment.

c) SCE calculation M-0012-036, "Postulated Transient Recirculation Flow From Refueling Water Storage Tanks" (Reference 1): This calculation ensures excess air does not enter the system from the RWST during recirculation mode switchover.

The calculation evaluates the potential for air ingestion through vortex formation or other mechanisms due to the assumed failure to close the RWST isolation valves post-Recirculation Actuation Signal (RAS).The calculation determines how far the potential air bubbles would travel in the piping before equilibrium with the containment sump is established and concludes that there is considerable margin such that the air would not reach the ECCS pumps.d) SCE calculation M-0012-039, "ESF [Engineered Safety Features]

Pump Suction with Entrained Air After RAS" (Reference 3): This calculation evaluates the potential impact of an air pocket traveling from the containment sump to the ECCS pumps. The air pocket could be trapped in the short horizontal pipe section between the Containment Emergency Sump isolation valve and the elbow open to the sump. The air would be transported into the vertical piping section leading to the ECCS pump suction. The calculation conservatively assumes that the bubble will transport to the pumps and calculates transit time for an assumed 5% void fraction.e) SCE calculation M-DSC-370, "LPSI/HPSI Nitrogen Pocket Transient Analysis" (Reference 5): The calculation establishes water hammer limits for the ECCS discharge lines. This calculation is based on a postulated gas pocket of approximately 5 cubic feet, generated due to off-gassing of nitrogen-saturated water from the Safety Injection Tanks that leaks past the check valves. The calculation concludes that the piping and supports will withstand the potential water hammer that can occur upon ECCS pump start. This calculation Page 6 of 29 Attachment 2 established the current discharge acceptance criterion between the ECCS pumps and the outside containment isolation valves that is monitored by SIT level trending.f) Desktop Guide for Evaluation of Leak Rate and Gas Voiding in ECCS piping associated with HPSI or LPSI check valve leakage: This process describes how SIT leakage is evaluated.

The desktop guide uses Henry's law to calculate the rate of nitrogen coming out of solution based on the drop in SIT level. The resulting number is then evaluated against the amount of time the leakage will take to reach a volume of five (5) cubic feet of gas. Five cubic feet is based on the allowable amount of gas (Reference 5 and Item e above)to maintain the safety function of the system. This is then used to determine the header venting frequency to prevent the accumulation of unacceptable void volume.2. Results of the review of the new applicable gas volume acceptance criteria for each piping segment in each system where gas can accumulate where no acceptance criteria previously existed, Corrective Actions, and schedule for completion of the Corrective Actions: a) Pump Suction Piping SCE evaluated the potential void fraction to be within established industry guidance.The evaluation of pump suction piping demonstrates significant margin between the potential as-found void fraction and that allowed by the pump gas ingestion tolerance criteria.

The evaluation is documented as a change notice to SCE calculation M-0012-01D, "NPSH of ESF Pumps," (Reference 19).For the suction side of the ECCS pumps, conservative assumptions have been made for evaluation of the potential gas voids due to potential construction tolerance pipe slope (including valve bonnet pockets).

See Item 6 of this Design Evaluation for development of the potential voiding due to construction tolerance pipe slope.As the majority of the SONGS suction-side piping is 24-inches in diameter, application of Westinghouse Topical Report WCAP-1 6631, "Testing and Evaluation of Gas Transport to the Suction of ECCS Pumps" (Reference 29)was deemed to be potentially non-conservative.

Revision 0 of the WCAP covers testing of 6-inch and 8-inch piping.Therefore, an alternate conservative approach for the transport of gas voids was developed for SONGS working back from the interim pump acceptance criteria established in Westinghouse Report PA-SEE-450 Task 2, "Pump Gas Page 7 of 29 Attachment 2 Ingestion Tolerance Criteria," (Reference

32) which identifies the ingestion limits to be employed by member utilities.

The interim criteria, which address pump mechanical integrity only, are as follows: Single-Stage Multi-Stage Multi-Stage Stiff Shaft Flexible Shaft Steady-State 2% 2% 2%Transient*

5% for 20 20% for 20 sec. 10% for 5 sec.sec.QB.E.P. Range 70%-120% 70%-140% 70%-120%Pump Type WDF CA RLIJ, JHF (transient data)* The transient criteria are based on pump test data and vendor supplied information.

For the SONGS ECCS pumps, the single-stage and stiff-shaft multi-stage criteria are applicable (LPSI and CS pumps are single stage, HPSI pumps are stiff shaft and multi-stage);

each has criteria for a transient time period of 20 seconds. An assumption was made that the potential voids for horizontal piping at a given elevation would pass through the pumps in the critical 20 second transient timeframe; if it were instead assumed that the void was transported over a longer period of time, the void fraction would be reduced.The largest resultant 20-second transient void volume fraction is approximately 1.8%, well below the transient ingestion tolerance criteria of 5% for the single-stage LPSI and CS pumps, and the transient ingestion tolerance criteria of 20% for the multi-stage HPSI pumps. It should also be noted that the transient void fraction is lower than the allowable steady-state void fraction of 2%. This void fraction was calculated at a flow rate corresponding to a Froude number of 0.55, which is considered to be the minimum flow rate for the evaluation.

The selection of a Froude number of 0.55 as a cut-off point is consistent with the minimum flow rate evaluated in WCAP-16631, "Testing and Evaluation of Gas Transport to the Suction of ECCS Pumps" (Reference 29).SCE calculation M-0012-01D, "NPSH of ESF Pumps," (Reference 19)documents this evaluation, including the assumed impact on pump available Net Positive Suction Head (NPSH) in accordance with NUREG / CR-2792 (Reference 30).b) Pump discharge piping downstream of the pump to the first isolation valve SCE maintains a SONGS-specific transient analysis, SCE calculation M-DSC-370 (Reference 5). The analysis was expanded to include the water Page 8 of 29 Attachment 2 hammer impact of two LPSI pumps acting on a 16 feet of 8-inch piping (approximately 5 cubic feet) void and containment spray discharge piping.The analysis demonstrates that the assumed gas void can be accommodated upon pump start without water hammer damage to piping or supports.

The calculation analyzes the HPSI and Containment Spray piping, showing that the forces on the LPSI piping bound the potential void that could be formed.The calculation also addresses potential voiding due to construction tolerance pipe slope. The additional potential voiding does not change the conservative assumptions for the water hammer due to pipe voiding caused by Safety Injection Tank check valve leakage. See Item 6 of this Design Evaluation for development of the potential voiding due to construction tolerance pipe slope.c) Pump discharge piping downstream of the first isolation valve i. Containment Spray, downstream of the outside containment isolation valve: SCE calculation M-DSC-041, "Containment Spray Rings Dynamic Stress Analysis for Hydraulic Transients," (Reference 28)evaluates the impact on the Containment Spray rings due to a partially filled header downstream of the containment spray isolation, concluding that damage would not occur.ii. Hot leg injection, downstream of the outside containment isolation valves: The water hammer evaluation for potential gas voids accumulating in the hot leg injection piping downstream of the containment isolation valves was performed in accordance with Westinghouse Report PA-SEE-450 Task 1, "Methodology for Evaluating Waterhammer in the Containment Spray Header and Hot Leg Switchover Piping," (Reference

31) evaluating hot leg injection.

These gas voids could develop during the period that the hot leg is drained of fluid following a large break Loss of Coolant Accident (LOCA). On switch-over from cold leg to cold/hot leg injection, the developed gas void would not result in a water hammer. The PWROG report specified that for Combustion Engineering (CE) plants, since the hot leg injection piping enters the hot leg from the bottom of the pipe, no gas void is developed in the hot leg which could cause a water hammer. The bottom entry was confirmed by review of SONGS piping isometrics for the hot leg injection piping (Drawings S2-1201-ML-018 Sh 1, $2-1201-ML-016 Sh 1 -Reference 47).iii. Cold leg injection, downstream of the outside containment isolation valves: A water hammer evaluation for potential gas voids accumulating in the cold leg injection piping downstream of the containment isolation valves was performed for Combustion Engineering plant designs in CE Report FAI/08-137, "Generic Criterion for Cold Leg Injection Gas-Waterhammer" (Reference 54). The report Page 9 of 29 Attachment 2 concluded that the two potential sources are air that has not been vented or flushed and nitrogen coming out of solution between isolation and check valve. SCE sweeps the EGOS piping to ensure these sections do not have significant voids remaining following maintenance, or outage refilling activities per Procedure S023-3-2.6,"Shutdown Cooling System Operation" (Reference 43).For nitrogen coming out of solution, a bubble would be compressed against a check valve. The pressure needed to compress the bubble would open the check valve to push a limited amount of water/gas into the downstream region. This would preclude the initiation of a water hammer (Reference 54).d) RCS Allowable Gas Ingestion The PWROG qualitatively evaluated the impact of non-condensable gases entering the RCS on the ability on the post-accident core cooling functions of the RCS in Westinghouse Report PA-SEE-450 Task 3, "Non-condensable Gas Voids in EGGS Piping; Assessment of Potential Effects on Reactor Coolant System Transients Including Chapter 15 Events," (Reference 33).This evaluation assumed that five (5) cubic feet of non-condensable gas at 400 psia was present in the high pressure safety injection system discharge piping concurrent with 5 cubic feet of non-condensable gas at 100 psia in the low pressure safety injection system discharge piping. The qualitative evaluation concluded that the quantities of gas had no adverse impact on core cooling.The allowable gas accumulation in any section of the SONGS low pressure safety injection system cold leg piping was verified to be less than 5 cubic feet of non-condensable gas at 100 psia at any location.

The allowable gas accumulation in any section of the SONGS high pressure safety injection cold leg and hot leg piping was verified to be less than 5 cubic feet of non-condensable gas at 400 psia at any location.

A summary of the applicability is documented in Notification 200004023, Task 23 (Reference 37).3. Summary of the changes to the design basis documents, Corrective Actions, and schedule for completion of the Corrective Actions: The following changes were made to design basis documents in response to GL 2008-01: a) SCE calculation M-0012-036, "Postulated Transient Recirculation Flow From Refueling Water Storage Tanks" (Reference 1)- During the GIL 2008-01 review, it was determined that the calculation was overly conservative, in that it assumed for a single-failure scenario both RWSTs would continue to drain down at the same rate due to the cross-connect piping. As the cross-connect Page 10 of 29 Attachment 2 piping is well above the level where potential air ingestion could occur, the amount of air-entrained water that could be drawn into the suction line for every inch of level decrease between the point at which potential vortexing ensues and the point at which the suction is broken is half of that assumed in the calculation.

The calculation assumed that potential vortexing could occur at water levels less than 2 inches above the bottom of the down-turned RWST suction elbow.SCE engaged Creare Inc. to independently determine this submergence level as a means to validate this key calculation assumption.

Creare Report TM-2791A, "SONGS Air Management From RWST and CES [Containment Emergency Sump]," (Reference

2) recommends use of 3 inches of submergence for the onset of potential air entrainment.

The net result of the two above-described changes is a decrease in the amount of air-entrained water that could enter the suction line; this increases the margin, further ensuring that the ECCS pumps will not be impacted by the potential air ingestion.

A change notice to Revision 3 of the calculation (Reference

1) was issued. The supporting Creare Report (Reference

2) was issued on July 31, 2008.b) SCE calculation M-0012-039, "ESF Pump Suction with Entrained Air After RAS" (Reference 3): SCE engaged Creare Inc. to independently assess the potential for the air pocket to transport to the pumps. Creare Report TM-2791A, "SONGS Air Management From RWST and CES," (Reference 2)concludes that based on the time required to open the valve and transition the pump suction from the RWST to the CES, the air pocket will escape back through the CES top-hat screens. Even if residual air were to remain at the top of the piping, the low Froude number (- 0.325 at pump run-out flows)would preclude transport downward through the piping to the pumps. The Creare Report (Reference

2) was issued on July 31, 2008. The SCE calculation (Reference

3) was subsequently superseded by Reference 2.c) Desktop guide for evaluation of Leak Rate and Gas Voiding in ECCS piping associated with HPSI or LPSI check valve leakage: To formally document the relationship between the drop in Safety Injection Tank water level and the amount of nitrogen coming out of solution due to check valve leakage, SCE calculation M-0013-005, "Safety Injection Tank Fluid Nitrogen Evolution" (Reference

4) was generated.

Revision 0 of the calculation was issued on August 18, 2008.d) SCE calculation M-DSC-370, "LPSI/HPSI Nitrogen Pocket Transient Analysis" (Reference 5): A change notice to Revision 0 of the calculation was issued to encompass the full range of pump operating scenarios.

Page 11 of 29 Attachment 2 4. Results of the system P&ID and isometric drawing reviews to identify all system vents and high points: Based on a review of plant isometric drawings, minor differences in piping lengths and configuration were identified between SONGS Units 2 and 3. A single GL 2008-01 evaluation was performed to bound both units. The analysis of the differences between Units 2 and 3 and the adjustments made in the GL 2008-01 evaluation are documented in Notification 200004023, Sub-Order 800072776 (Reference 21).SCE maintains design-controlled isometric drawings for the piping systems covered by the Generic Letter. A review of these isometric drawings and the Piping and Instrument Diagrams (P&IDs) was conducted to identify system high points, including intermediate inverted "U" segments, in order to confirm that vents were appropriately located. An intermediate inverted "U" segment in the HPSI Train "A" discharge piping on both Units 2 and 3 was found to not have a vent. Notification 200128967, Task 1 (Reference

36) documents the resulting operability determination, indicating that the piping segments had been swept of gas by recirculating water through the header for a Safety Injection Tank fill.Piping elevation diagrams were generated based on the P&IDs and isometric drawings to illustrate the ECCS systems in vertical orientation as working drawings to facilitate the Generic Letter evaluation.

These diagrams include the elevations of piping, piping length, and applicable piping components, including vent valves.5. Identification of new vent valve locations based on the drawing review, Corrective Actions, and schedule for completion of the Corrective Actions: Based on the drawing review described above, an inverted "U" piping segment in one train of the HPSI discharge piping was identified as not containing a vent valve. Notwithstanding that this line had been swept during SIT fill as discussed in Item 4 above, a vent valve will be added in each unit to allow this portion of the line to be conventionally filled and vented should the line require draining for maintenance.

The addition of the valves will be tracked as a Corrective Action resulting from the Generic Letter evaluation, Notification 200128967, Order 800163628 (Reference 48). The vent valves are planned to be added no later than the U2C16 and U3C16 outages scheduled for the fall of 2009 and 2010, respectively.

See Section B, Item 4, of this Attachment.

6. Results of the system confirmation walkdowns that have been completed for the portions of the systems that require venting to ensure that they are sufficiently full of water: SCE performed the Generic Letter evaluation based on construction tolerances, assuming the ECCS piping was installed with sloping that could trap gas voids.Page 12 of 29 Attachment 2 The results of the evaluation were well within established industry guidance (Item 2 of this Design Evaluation) in demonstrating that the piping systems are sufficiently full of water. Confirmatory walkdowns will be conducted to verify that the as-built piping configuration supports the evaluation assumptions.

At the time of original construction, piping fabrication and installation were controlled by Construction Specification CS-P204, "Field Fabrication and Erection of Nuclear Piping to ASME Section III and Field Fabrication and Erection of Auxiliary Boiler External Piping to ASME Section I, Rev. 10 (Reference 8). Fabrication and installation of pipe supports were controlled by CS-P207, "Construction Specification for Pipe Support Field Fabrication and Installation," Rev. 15 (Reference 52). Field Quality Control (QC) walked down and inspected each line to ensure that the as-built configuration matched the drawings within the allowable construction tolerances.

NRC IE Bulletin No. 79-14, "Seismic Analyses for As-Built Safety-Related Piping Systems," issued July 2, 1979, required licensees to review as-built safety-related piping to verify that seismic analyses were applicable to the as-built conditions.

SCE's response to Bulletin No. 79-14 was transmitted to the NRC on November 6, 1979 (Reference 9). As SONGS Units 2 and 3 were under construction at the time the bulletin was issued and the response was prepared, SCE reviewed the then-current status of the design of all safety-related Category I piping and concluded that the design procedures, construction tolerances, and Field QC inspection adequately ensured compatibility between the design basis input used in the seismic analyses and the as-built configuration of the piping systems.Following completion of construction, SCE performed walkdowns to verify that the as-built configuration remained in accord with the seismic analyses.

The walkdown / verification program is documented for Unit 2 in M-DSC-075 (Reference 11), issued on January 26, 1982, and for Unit 3 in M-DSC-077 (Reference

12) issued on February 24, 1983.Although the piping has been previously verified to have been installed in accordance with the design, the Generic Letter evaluation was performed applying slope to the piping in a direction that could trap gas pockets. Using piping fit-up allowances of up to 2 inches as called out in Construction Specification CS-P204 (Reference 8), piping slopes (inches/foot) were determined and applied to all horizontal pipe runs within the scope of the Generic Letter. For piping runs where the accumulated slope was determined to be less than % inch, 3/4 inch was conservatively applied. The methodology used in determining the slope and resultant void volumes for a given section of pipe is contained in SCE report, "SONGS Methodology for Evaluation of Piping Voids" (Reference 13), and the application of the methodology to each horizontal section of pipe is documented in Notification 200004023, Task 15 (Reference 22).Page 13 of 29 Attachment 2 The potential void volumes were calculated as described above and then evaluated to ensure that they did not pose challenges from either a pump operability or water hammer perspective.

See Item 2 of the Design Evaluation for a summary of the pump operability and water hammer evaluations.

At the time of the three-month supplemental response, SCE did not anticipate performing additional confirmatory walkdowns.

To be consistent with current industry expectations, SCE has decided to perform walkdowns utilizing laser scanning to confirm the slope assumptions used in the evaluation.

Piping runs that have the greatest influence on the evaluation (i.e., the pump suction void fraction) will be scanned. Piping runs that have a low influence on the evaluation will be sampled. Due to the conservative methodology applied in the evaluation described above, any differences found during the walkdowns are not expected to change the evaluation results. Walkdowns of accessible and inaccessible piping in Units 2 and 3 are not complete.

These confirmatory walkdowns will be tracked as Corrective Actions. See Section B, Items 7 and 8 of this attachment.

7. Identification of new vent valve locations resulting from walkdowns:

Walkdowns were conducted confirming that the inverted "U" sections in the, HPSI Train "A" discharge piping identified during the drawing review do not have vents.As discussed in Item 5 above, new vent valves will be added in this location on each unit as documented in Notification 200128967 (Reference 48).8. Results of the review of the fill and vent activities and procedure reviews for each system: Plant procedures and associated drawings were reviewed for verification that appropriate vents are used during the fill and vent activities to purge gas from the Safety Injection, Shutdown Cooling, and Containment Spray systems. The reviews are documented in Notification 200004023, Task 16 (Reference 18), Notification 200004023, Task 2 (Reference 34), and Notification 200004023, Task 32 (Reference 26).The following procedures ensure that the Safety Injection, Shutdown Cooling, and Containment Spray Systems are properly filled and vented following maintenance activities or shutdown, and prior to return to service: S023-3-2.7, Safety Injection System Operation (Reference 14)S023-3-2.7.2, Safety Injection System Removal/Return to Service Operation (Reference 15)S023-3-2.9, Containment Spray System Operation (Reference 16)S023-3-2.6, Shutdown Cooling System Operation (Reference 43)S023-11-1, "Filling and Venting Transmitters and Sensing Lines and Verification of Sensing Line Valve Position" (Reference 50), also ensures that Safety Page 14 of 29 Attachment 2 Injection System instrument transmitters and sensing lines have been filled and vented following outages or other maintenance.

Regardless of changes in work scope, the procedures for returning the subject systems to service assume the piping is completely drained and directs that all lines and components be filled with system fluid and vented of gas. Instructions to use the appropriate fill and vent attachments prior to equipment return to service are provided in the standard Work Authorization Record (WAR). Venting is performed by starting at the source and working sequentially toward systems loads. Prior to returning the ECCS or CS to service, the suction piping is vented and the pumps run on miniflow per procedure S023-3-2.7.2 (Reference 15).9. Identification of procedure revisions or new procedures resulting from the fill and vent activities and procedure reviews that need to be developed, Corrective Actions, and schedule for completion of the Corrective Actions: Three procedure revisions were identified as a result of the Generic Letter evaluation:

a) While the HPSI discharge piping is effectively swept of gas during check valve testing and SIT filling activities, procedure S023-3-2.7.2, "Safety Injection System Removal/Return to Service Operation (Reference

15) will be revised to include sweeping of the inverted "U" sections in the HPSI Train "A" discharge piping (identified in Item 5 above) during plant restart until new vents are installed.

The procedure revision will be tracked as a Corrective Action resulting from the Generic Letter evaluation and is planned to be completed prior to restart of the unit for the Unit 3 Cycle 15 Refueling outage.See Section B, Item 2, of this Attachment.

b) Procedure S023-3-3.8, "Safety Injection Monthly Tests," (Reference 17)specifies that one of the objectives is to vent accessible valves on the discharge side. The procedure vents valves on both the suction and discharge sides and vents valves deemed necessary to ensure that the system is sufficiently full without limitations imposed by accessibility.

The procedure objective will be revised for clarification only. The procedure revision will be tracked as a Corrective Action resulting from the Generic Letter evaluation and is planned to be completed prior to restart of the unit for the Unit 3 Cycle 15 Refueling outage. See Section B, Item 3, of this Attachment.

c) With the addition of the vent valves discussed in Item 5 above, the appropriate procedure will be revised to include the new valves in the return to service fill and vent. This will be tracked as a part of the Engineering Change Package that will add the valves and will not be tracked here as a separate Corrective Action.Page 15 of 29 Attachment 2 10. Discussion of potential gas intrusion mechanisms into each system for each piping segment that is vulnerable to gas intrusion:

The following key potential gas intrusion mechanisms were evaluated in response to the Generic Letter: a) Air ingestion due to vortexing in the RWST in the suction-side piping: As discussed above, the key assumption regarding submergence of the suction nozzle in the RWST to preclude air ingestion was reviewed by Creare Inc., and SCE calculation M-0012-036 (Reference

1) was revised accordingly.

The conclusion reached remains that air potentially entrained in the water will not reach the check valves in the RWST suction line, and therefore will not reach the EGGS pumps.b) Air ingestion due to trapped air volume in the CES in the suction-side piping: As discussed above, SCE commissioned Creare Inc. to evaluate the potential for the air pocket trapped between vertical filled piping and the CES valve to transport to the EGGS pumps. Creare Inc. concluded in its report (Reference

2) that the air pocket will escape back through the CES top-hat screens, and that even if residual air were to remain, the low Froude number (- 0.325 at pump run-out flows) would preclude transport downward through the piping to the pumps.c) Air remaining following fill and vent activities due to construction tolerance sloping of piping, in both the suction side and discharge side: As described previously and documented in Reference 13, the construction tolerance was applied to each horizontal run of pipe, and the gas voids were summed for each piping elevation.

d) Potential air remaining in valve bonnets and orifices:

The methodology used in determining the void volumes for these piping components is contained in SCE report (Reference 13), and the application of the methodology to each component is documented in a series of Notifications (References 23, 24, and 25).e) Off-gassing through depressurization of nitrogen-saturated water from the Safety Injection Tanks: As described in the Testing Evaluation section below, the quantity of accumulated gas due to leakage through check valves in the discharge-side piping is managed by monitoring the Safety Injection Tank inventory and increasing periodic venting activities, as required, to preclude potential water hammer damage.f) Air ingestion due to lifting of the Low Temperature Over-Pressure (LTOP)relief valve, when initiating shutdown cooling (SDC) system operation:

The potential for a pressure spike occurring due to a gas-void induced water hammer when initiating SDC was reviewed.

The evaluation, documented in Page 16 of 29 Attachment 2 Notification 200004023, Task 3 (Reference 20), concludes that based on system operating pressures and valve stroke times, a pressure spike during SDC entry that could cause the LTOP to lift is not expected to occur.g) Introduction of water containing dissolved gases from high pressure systems interfacing with the ECCS piping: The high pressure Reactor Coolant (RC)and Chemical and Volume Control (CVC) Systems interface with the lower pressure ECCS and CS suction and discharge piping. These interfaces were evaluated to determine the potential for leakage through the valve configurations that serve as interface boundaries between these systems.The evaluations determined that interfaces between these systems were formed by either two or three isolation gate valves in series. The major gas component in the interfacing system fluid is hydrogen in either the RC or the CVC System fluid. The molar hydrogen concentration in the interfacing fluid is approximately 10 times lower than the expected nitrogen molar concentration in the Safety Injection Tanks. Therefore substantial leakage would not occur through these in-series isolation valve configurations and hydrogen concentrations.

Notification 200004023, Task 6 (Reference 51)provides the basis for determining that evolution of hydrogen is not expected, and should it occur, would have an insignificant impact on the operation of the ECCS and CSS.h) In-leakage through vent valves when the local system pressure is less than atmospheric:

ECCS pumps are located at lower elevations in the plant in order to provide positive pressure to the suction of the pumps. While taking suction from the RWST, the suction pressure would not decrease below atmospheric.

Additionally, SONGS performs static venting of ECCS pumps before running and does not perform venting while the pump is running.i) Conditions where local temperatures are at or above saturation temperature:

The suction connection with the CES upon recirculation initiation is the only potential flashing location in the ECCS. The predicted head loss across the emergency sump screens, including chemical effects, exceeds the submergence of the top portion of the screens. At high water temperatures, a small amount of containment over-pressure is credited such that the local temperature remains below the saturation temperature, thereby precluding flashing.

Details are provided in SCE's supplemental response to NRC Generic Letter 2004-02 (Reference 35).11. Ongoing Industry Programs Ongoing industry programs are planned in the following areas which may impact the conclusions reached during the Design Evaluation of SONGS relative to gas accumulation.

The activities will be monitored to determine if additional changes to the SONGS design are required or desired to provide additional margin.Page 17 of 29 Attachment 2 Gas Transport in Pump Suction Piping The industry has initiated testing to provide additional knowledge relative to gas transport in large diameter piping. WCAP-16631 "Testing and Evaluation of Gas Transport to the Suction of ECCS Pumps," (Reference

29) reports the results of testing performed for gas transport in 6-inch and 8-inch piping.Additional testing will be performed for gas transport in 4-inch and 12-inch low temperature systems and 4-inch high temperature systems. This program will also perform a scaling study integrating the results of the 4-inch, 6-inch, 8-inch, and 12-inch testing.Pump Acceptance Criteria Long-term industry tasks have been initiated that will provide additional tools to address GL 2008-01 with respect to pump gas void ingestion tolerance limits.Page 18 of 29 Attachment 2 Testing Evaluation

1. Results of the periodic venting or gas accumulation surveillance procedure reviews: Periodic venting activities are conducted to purge nitrogen from the HPSI and LPSI piping and are governed by procedure S023-3-3.8, "Safety Injection Monthly Tests" (Reference 17). The procedure covers venting valves in the Safety Injection System and was reviewed for verification that all applicable high point vents are used to purge gas from the system. This review is documented in Notification 200004023, Task 16 (Reference 18).Procedure S023-3-3.8, "Safety Injection Monthly Tests'" (Reference 17), performs a monthly surveillance of ECCS piping to ensure that it is filled and vented as required by the Technical Specifications.

If five (5) seconds of gas is found in this piping, then a Notification is written for Engineering Evaluation (Corrective Action Program).

The 5-second interval is used for historical data and is based on experience trending the SIT levels. It is not a quantitative acceptance criterion for the surveillance; it is a trigger to review the surveillance frequency and evaluate the leakage.For gas found in the discharge piping near the containment penetration, the source is known to be nitrogen coming out of solution as high pressure nitrogen saturated water from the Safety Injection Tanks depressurizes across the leaking check valve. Engineering has developed a method to conservatively quantify the amount of gas vented in this instance.

An accurate leak rate is determined by trending the SIT levels, utilizing data from the plant computer, and calculating the volume of nitrogen released in depressurization.

The rate of accumulation of nitrogen is then compared to the allowable void size (5 cubic feet) assumed in the transient analysis (Reference 5). If the leak rate is such that the critical void size will be reached before the 31-day surveillance interval, Engineering directs Operations to either attempt to reseat the check valve or increase the frequency of the charged piping surveillance.

The above-described monitoring of SIT level and adjustment in venting frequency is administratively controlled by a desktop guide.2. Identification of procedure revisions or new procedures resulting from the periodic venting or gas accumulation surveillance procedure reviews that need to be developed, Corrective Actions, and schedule for completion of the Corrective Actions: A new Engineering procedure will be developed to formalize the monitoring of SIT level discussed in Item 1 above in order to determine the amount of leakage into the header of the ECCS System. This new procedure will be tracked as a Corrective Action resulting from the Generic Letter evaluation and is planned to Page 19 of 29 Attachment 2 be issued no later than 90 days after completion of the U3 Cycle 15 refueling outage. This date is commensurate with the fact that SCE will continue to monitor SIT level per desktop guidance.

See Section B, Item 5, of this Attachment.

3. Results of the review of how procedures adequately address the manual operation of the SDC system in its decay heat removal mode of operation, including how the procedures assure that the SDC system is sufficiently full of water to perform its decay heat removal safety function (high point venting) and how pump operation is monitored by plant personnel (including a description of the available instrumentation and alarms): Procedure S023-3-2.6, "Shutdown Cooling System Operation," (Reference 43)provides instruction for starting up, operating, and terminating the SDC system.Procedure S023-3-2.6.1, "Shutdown Cooling Operation on Containment Spray," (Reference

44) provides direction for using the CS pumps for shutdown cooling and transfer between the LPSI and CS pumps for SDC operation.

These procedures were reviewed for adequacy in providing filling and venting guidance to ensure that the system is full of water to perform its decay heat removal safety function.For normal operation, prior to placing the shutdown cooling system in service, the SDC suction line, warm-up bypass line, and shutdown cooling heat exchangers are vented at the high point vents to ensure the line is full. The SDC crosstie line, which is the CS pumps suction piping from the RCS, and the CS pumps are vented prior to CS shutdown cooling alignment.

Procedure S023-3-2.6, "Shutdown Cooling System Operation," (Reference 43)also provides adequate guidance to fill and vent the system after maintenance, prior to placing the system in service. The process involves an initial static system vent, where the system is vented from the system high points to the pump, followed by a system sweep using a LPSI pump.SDC flow conditions are monitored using the following indications:

Fl 0306, SDC flow indicator:

Control room indication PCS/CFMS PID F306: Plant Computer point ID The LPSI and CS pump amps are monitored using the following indications:

LPSI/CS pump motor amperage at associated hand switch: Control room indication PCS/CFMS PIDs HS-9390 and HS-9391: Plant Computer point ID This review concludes that the SDC procedures provide adequate guidance to ensure the system is sufficiently full of water to maintain SDC system operability.

Page 20 of 29 Attachment 2 4. Summary of the results of the procedure reviews performed to determine that gas intrusion does not occur as a result of inadvertent draining due to valve manipulations specified in the procedures, system realignments, or incorrect maintenance procedures:

SCE reviewed the applicable procedures and current work processes to ensure gas intrusion does not occur as the result of inadvertent draining.Maintenance is planned and performed within established work boundaries.

Procedures are in place for the return to service of the pumps and suction piping (Reference 15). Additionally, the pumps are run afterward to verify adequate filling and venting. Discharge piping is filled and vented on a case-by-case basis, depending on the scope of the work.The review of periodic venting surveillances did not identify testing, maintenance, or operational procedures that have caused the ECCS, CSS, or SDCS to be drained inadvertently under plant conditions requiring these systems to be functional.

If a system was found inadvertently drained, a plan would be developed to return the system to a filled condition by filling and venting the system by starting at the source and working sequentially toward system loads.See Notification 200004023, Task 16 (Reference 18).5. Description of how gas voids are documented, dispositioned, and trended, if found in any of the subject systems: The amount of gas assumed to be in the EGGS discharge headers is quantified by monitoring SIT level. Appropriate actions are taken (described in Item 1 above) to ensure the system maintains an operable status by increased venting of the header with a leaking check valve. Monitoring SIT leakage allows SCE to anticipate and quantify gas accumulation.

This method also helps to detect degrading conditions prior to challenging the operability of the EGGS.In addition to monitoring SIT level, any vent that releases more than five (5)seconds of gas is entered into the Corrective Action Program and evaluated and dispositioned by Engineering.

This evaluation is only used to confirm information already gathered from monitoring of SIT level.SCE has recognized the significance of gas coming out of solution in the EGGS headers since 1999. SCE has routinely replaced check valves with in-kind, bench-tested replacements in order to attempt to minimize the leakage; two valves will be replaced in-kind in the U3C15 outage scheduled for October 2008.Prior to the issuance of GL 2008-01, SGE planned to install new soft-seated check valves designed to reduce the amount of gas intrusion (back leakage) from Page 21 of 29 Attachment 2 the SITs. The new valves are being phased in as maintenance replacements for the existing valves.Page 22 of 29 Attachment 2 Corrective Actions Evaluation

1. Summary of the results of the reviews regarding how gas accumulation has been addressed:

SCE performs a monthly surveillance of ECCS piping to ensure that it is filled and vented as required by the Technical Specifications.

If five (5) seconds of gas is found in this piping, then a Notification is written into the Corrective Action Program for Engineering Evaluation.

The amount of gas assumed to be in the ECCS discharge headers is quantified by monitoring SIT level. Appropriate actions are taken to ensure the system maintains an operable status by increased venting of the header with a leaking check valve.For additional discussion, see Testing Evaluation, Item 5.2. Items that have not been completed, schedule for their completion, and the basis for that schedule: No changes to SCE's Corrective Action Program are being made as a result of the Generic Letter evaluation.

Page 23 of 29 Attachment 2 B.

SUMMARY

OF CORRECTIVE ACTIONS AND SCHEDULE All identified corrective actions will be tracked per the Corrective Action Program (CAP). The due dates are commensurate with plant need and safety significance of resolution.

Item Corrective Action Due Date 1. Technical Specification Bases for SR 3.5.2.4 90 days after completion of will be revised to read "Maintaining the piping the Unit 3 Cycle 15 from the RWST to the RCS full of water..." Refueling outage (scheduled for October 2008)2. Procedure S023-3-2.7.2, "Safety Injection Prior to restart of the unit for System Removal/Return to Service Operation," the Unit 3 Cycle 15 (Reference

15) will be revised to include Refueling outage (scheduled sweeping of the inverted "U" sections in the for October 2008)HPSI Train "A" discharge piping during plant restart until new vents are installed.

3. Procedure S023-3-3.8, "Safety Injection Prior to restart of the unit for Monthly Tests" (Reference

17) specifies that the Unit 3 Cycle 15 one of the objectives is to vent accessible Refueling outage (scheduled valves on the discharge side. The procedure for October 2008)vents valves on both the suction and discharge sides and vents valves deemed necessary to ensure that the system is sufficiently full without limitations imposed by accessibility.

The procedure objective will be revised for clarification only.4. A vent valve will be added to the Train "A" U2C16 and U3C16 outages discharge piping of the high pressure safety scheduled for the fall of 2009 injection pumps in each unit. and 2010, respectively

5. An Engineering procedure will be developed to 90 days after completion of formalize SIT monitoring to provide a formal the Unit 3 Cycle 15 process of quantifying leakage into the low Refueling outage (scheduled pressure side of the Safety Injection system. for October 2008)Continues on next page Page 24 of 29 Attachment 2 Item Corrective Action Due Date 6. SCE is continuing to support the industry and 1 year after NRC approval of NEI Gas Accumulation Management Team TSTF activities regarding the resolution of generic TS changes via the TSTF traveler process.Following NRC approval of this TSTF, SCE will evaluate adopting the TSTF to either supplement or replace current TS and LCS requirements.

7. SCE will conduct confirmatory walkdowns as 60 days after completion of identified in Item 6 of the Design Evaluation for the Unit 2 outage (scheduled Unit 2 accessible and inaccessible piping and for January 2009)submit a Nine-Month supplemental response with the results of these walkdowns and any resulting corrective actions.8. SCE will conduct confirmatory walkdowns as 60 days after completion of identified in Item 6 of the Design Evaluation for the Unit 3 Cycle 15 Unit 3 accessible and inaccessible piping and Refueling outage (scheduled submit a Nine-Month supplemental response for October 2008)with the results of these walkdowns and any resulting corrective actions.Page 25 of 29 Attachment 2 References

1. Calculation: "Postulated Transient Recirculation Flow From Refueling Water Storage Tanks," Southern California Edison; M-0012-036, Rev. 2 2. Report: "SONGS Air Management From RWST and CES," Creare Inc.; TM-2791A /S023-205-7-C139, Rev. 0. Report supersedes Reference

3.3. Calculation

"ESF Pump Suction with Entrained Air After RAS," Southern California Edison; M-0012-039, Rev. 0. Calculation superseded by Reference

2.4. Calculation

"Safety Injection Tank Fluid Nitrogen Evolution," Southern California Edison; M-0013-005, Rev. 0 5. Calculation: "LPSI/HPSI Nitrogen Pocket Transient Analysis," Southern California Edison; M-DSC-370, Rev. 0 6. Drawings:

Piping and Instrumentation Diagrams (P&IDs); Southern California Edison; Reference 47 includes a complete listing of P&IDs used in this evaluation.

7. Drawings:

Piping Isometrics; Southern California Edison; Reference 47 includes a complete listing of isometrics used in this evaluation.

8. Construction Specification: "Field Fabrication and Erection of Nuclear Piping to ASME Section III and Field Fabrication and Erection of Auxiliary Boiler External Piping to ASME Section I," Bechtel Power Corporation; CS-P204, Rev. 10 9. Letter: K.P. Baskin (SCE) to R.H. Engelken (NRC) dated November 6, 1979;

Subject:

IE Bulletin 79-14, et al, San Onofre Nuclear Generating Station Units 2 and 3 10. Not Used 11. Calculation: "As-Built Verification of Unit 2 Pipe Supports," Southern California Edison; M-DSC-075, Rev. 0 12.Calculation: "As-Built Verification of Unit 3 Pipe Supports," Southern California Edison; M-DSC-077, Rev. 0 13. Report: "SONGS Methodology for Evaluation of Piping Voids," Southern California Edison; Notification 200004023, Task 34 14. Procedure: "Safety Injection System Operation," Southern California Edison; S023-3-2.7, Rev. 22 Page 26 of 29 Attachment 2 15. Procedure: "Safety Injection System Removal/Return to Service Operation," Southern California Edison; S023-3-2.7.2, Rev. 16 16. Procedure: "Containment Spray System Operation," Southern California Edison;S023-3-2.9, Rev. 24 17. Procedure: "Safety Injection Monthly Tests," Southern California Edison; S023-3-3.8, Rev. 20 18. Notification:

Review of fill and vent and procedures; Southern California Edison;Notification 200004023, Task 16 19.Calculation: "NPSH of ESF Pumps," Southern California Edison; M-0012-01D, Rev.2 20. Notification:

Review of potential for gas-void induced water hammer to cause LTOP to lift; Southern California Edison; Notification 200004023, Task 3 21. Notification:

Review of Unit 2 and Unit 3 piping, and adjustments for a bounding evaluation; Notification 200004023, Sub-Order 800072776 22. Notification:

Application of report, "SONGS Methodology for Evaluation of Piping Voids," (Reference

13) to determine potential voids due to construction tolerance pipe slope and to generate piping elevation diagrams; Notification 200004023, Task 15 23. Notification:

Application of report, "SONGS Methodology for Evaluation of Piping Voids," (Reference

13) to determine potential voids in valve bonnets; Notification 200004023, Task 14 24. Notification:

Application of report, "SONGS Methodology for Evaluation of Piping Voids," (Reference

13) to determine potential voids due to piping reducers;Notification 200004023, Task 22 25. Notification:

Application of report, "SONGS Methodology for Evaluation of Piping Voids," (Reference

13) to determine potential voids due to orifices; Notification 200004023, Task 18 26. Notification:

Review of procedures to assess potential voids due to filling and venting of pumps; Notification 200004023, Task 32 27. Not Used 28. Calculation: "Containment Spray Rings Dynamic Stress Analysis for Hydraulic Transients," Southern California Edison; M-DSC-041, Rev. 0 Page 27 of 29 Attachment 2 29. Westinghouse Topical Report: "Testing and Evaluation of Gas Transport to the Suction of ECCS Pumps," PWROG; WCAP-16631, Rev. 0 30. Report: "An Assessment of Residual Heat Removal and Containment Spray Pump Performance Under Air and Debris Ingesting Conditions," Office of Nuclear Reactor Regulation, U. S. NRC; NUREG / CR-2792 (Creare TM-825); September 1982 31. Report: "Methodology for Evaluating Waterhammer in the Containment Spray Header and Hot Leg Switchover Piping," PA-SEE-450 Task 1, PWROG Program 32. Report: "Pump Gas Ingestion Tolerance Criteria," PA-SEE-450 Task 2, PWROG Program 33. Report: "Non-condensable Gas Voids in ECCS Piping; Assessment of Potential Effects on Reactor Coolant System Transients Including Chapter 15 Events," PA-SEE-450 Task 3, PWROG Program 34. Notification:

Review of drawings associated with fill and vent and procedures; Southern California Edison; Notification 200004023, Task 2 35. Letter: R. Ridenoure (SCE) to Document Control Desk (NRC) dated February 27, 2008;

Subject:

Docket Nos. 50-361 and 50-362, NRC Generic Letter 2004-02, San Onofre Nuclear Generating Station Units 2 and 3, Attachment 1, Section 3.f.xiv 36. Notification:

Operability determination relative to inverted "U" piping segments not containing vent valves; Southern California Edison; Notification 200128967, Task 1 37. Notification:

Verification of void volumes relative to core cooling; Southern California Edison; Notification 200004023, Task 23 38. Not Used 39. Not Used 40. Not Used 41. Not Used 42. Procedure: "Work Clearance Application

/ Work Clearance Document / Work Authorization Record (WCA / WCD /WAR)," Southern California Edison; S0123-XX-5, Rev. 18 43. Procedure: "Shutdown Cooling System Operation," Southern California Edison;S023-3-2.6, Rev. 25 Page 28 of 29 Attachment 2 44. Procedure: "Shutdown Cooling Operation on Containment Spray," Southern California Edison; S023-3-2.6.1 Rev. 7 45.Action Request: 991000890, Installation of U2 Vent Valves 46.Action Request: 001200671, Installation of U3 Vent Valves 47. Notification:

List of drawings reviewed for GL 2008-01; Southern California Edison;Notification 200004023, Task 13 48. Notification:

Inverted "U" piping on HPSI Discharge; Southern California Edison;Notification 200128967, Order 800163628 49. Not Used 50. Procedure: "Filling and Venting Transmitters and Sensing Lines and Verification of Sensing Line Valve Position," Southern California Edison; S023-11-1, Rev. 11 51. Notification:

Review of High Pressure to Low Pressure System Interaction; Southern California Edison; Notification 200004023, Task 6 52. Construction Specification: "Construction Specification for Pipe Support Field Fabrication and Installation; CS-P207, Rev. 15 53. Not Used 54. Report: "Generic Criterion for Cold Leg Injection Gas-Waterhammer," FAI/08-137, Combustion Engineering Plant Program Page 29 of 29